In the operation of household refrigerators, it has been common practice in the immediate past to automatically defrost the freezer unit as frequently as three, four, or six times a day to prevent frost buildup on the refrigeration unit. In many household refrigerators an electrical heater is energized to defrost the refrigeration unit. With recent efforts to minimize electrical power consumption it is considered to be undesirable to defrost a household refrigerator as frequently as in the past. Consequently, defrost control timers that produce fewer defrost cycles, such as one per day, are increasingly popular. Yet, there may be special, irregularly occurring circumstances that make it desirable to defrost the refrigerator more frequently than once a day. Additionally, because of inherent weather and atmospheric differences at various geographic locations, frequent defrosting may be required in some locations while less frequent defrostings may be acceptable in other locations. A single defrost control system that can be operated to selectively provide many or just one defrost operations in a given time period would be useful to meet the diverse requirements mentioned above. Furthermore, it is desirable to provide this selective defrosting capability with a minimum physical and electrical change in existing refrigeration and defrosting equipment.